1. Field of the Invention
The present invention generally relates to instrumentation for taking measurements of the level of ultraviolet (UV) energy and, more particularly, to a portable UV intensity meter for measuring and displaying the intensity emitted by a UV light sources including, but not limited to, UV light sources used in spot curing systems.
2. Description of the Prior Art
There are many substances, known as monomers, which can be converted to polymers by chemical reactions. In some cases, these reactions are induced by chemical catalysts and initiators. However, polymerization can also be induced by supplying the initiation energy with visible or ultraviolet (UV) light. Such photochemical reactions have practical as well as theoretical advantages. For example, in certain manufacturing processes, a polymer may be used to secure parts of an assembly. In the field of fiber optics, splices and repairs are often made in the field using a polymer. In both of these examples, the photochemically induced polymerization is referred to as "curing".
Since there are many applications of UV cured polymers wherein the polymer is applied in only a small spot, there have been developed UV spot curing systems. These systems typically include a source of high intensity UV light which may be turned on and off by the operator and a flexible light guide which emits a small spot of UV light. The free end of the flexible light guide is positioned close to the applied monomer, and the power to the UV light source is turned on to initiate the photochemical curing polymerization process.
As UV spot curing has evolved, it has become increasingly important to establish a method of measuring system performance. Degradation of UV lamps, light guides, and reflectors can cause decreases in UV intensity and create curing problems. If the intensity of the UV light falls below a certain level, curing may not be complete resulting in a weak joint or attachment. Moreover, a visual inspection will not reveal the problem as the surface of the monomer spot may polymerize but the interior volume will not. It has therefore become mandatory, in certain applications to periodically measure the UV energy output of the spot curing system in order to insure that a sufficient UV intensity, is being delivered to the spot where curing is desired. However, such measurements are typically not conveniently made by current UV intensity measuring instruments and, due to the high output intensities of some spot curing systems, there is a risk that the output energy of the spot curing system will damage the measuring instrument.